Magnesium base alloy



Patented Nev. 12, 1940 UNITED STATES 2,221,253 MAGNESIUM BASE ALLOY Joseph D. Hanawalt and John 0.

land, Mich., assignors to The Midland, Mich., a corporation of Company, Michigan No Drawing.

McDonald, Mid- Dow Chemical Application November 13, 1939,

Serial No. 304,130

3 Claims.

Theinvention relates to magnesium base alloys. It more particularly concerns alloys of this nature having improved physical properties, such as high yield strength.

Commercially pure magnesium has been used in a limited way as a structural material because of its relatively low strength, although its light weight is a highly desirable characteristic.

It is, therefore, the principal object of the invention to provide an alloy of magnesium which utilizes the light weight characteristic of the magnesium and at the same time possesses superior strength properties.

Other objects and advantages will be apparent as the description of the invention proceeds.

Our invention resides in the discovery that magnesium base alloys composed of from 0.05 to 1.0 per cent barium and from 0.1 to 3 per cent of manganese, the balance being substantially all magnesium, is endowed with the afore-mentioned properties. While the property of high strength is manifest over the entire range of composition indicated, we have found that in general the preferred combination of properties, such as the most desirable yield strength coupled with good tensile strength, is found in those alloys containing from about 0.1 to 0.4 percent of barium and from 1 to 3 per cent of manganese.

A preferred alloy having exceptionally high yield strength as well as good tensile strength is one containing about 2 per cent of manganese and 0.2 per cent of barium. As an illustration of the improved properties of the above alloy, annealed specimens of rolled sheet made from this alloy were tested and found to have an average yield strength of 22,000 pounds per square inch. A specimen of sheet in the cold rolled state made from the preferred alloy was found to have a yield strength of 24,000 pounds per square inch. In comparison with our new ternary alloy, the parent binary magnesium alloy containing magnesium and manganese had the following properties: A sheet made from the binary magnesium-manganese alloy containing 2 per cent of manganese had in the annealed state a yield strength of only 19,000 pounds per square inch, while in the cold rolled state the yield strength of the binary alloy in this form was 0 23,000 pounds per square inch. The other parent binary alloy, viz. magnesium-barium, containing 0.2 per cent barium has a yield strength of only 16,000 pounds per square inch in the annealed state, while in the cold rolled state it had a yield strength of only 22,000 pounds per square inch. Similarly the yield strength of our new ternary alloy shows improvement over that of commercially pure magnesium treated in a similar manner. It will be noted from the above comparison that the properties of our new ternary alloy show a high degree of improvement over those of the related binary magnesium alloys. Similarl throughout the range of added alloying ingredients, improved strength characteristics will be observed. In addition, besides having desirable strength characteristics, the new ternary alloy is highly resistant under corrosive conditions.

The properties set forth above-under the term in the annealed state were obtained by first rolling the alloys at a temperature between about 600 to 800 F. and thereafter annealing them at various temperatures through a range of from 400 to 800 F. The properties selected were those of the annealed specimens, which in the tension tests exhibited the maximum elongation. The properties set forth under the term cold rolled were obtained by subjecting specimens of the alloys which had first been hot rolled at a temperature of from 600 to 800 F. to additional rolling in the cold'state, i. e. room temperature, to bring about a total reduction in thickness of from 2 to 10 per cent. The properties selected were those of the cold rolled specimens which showed the greatest tensile and yield strengths, while having at least 1 per cent elongation in 2 inches.

While the new alloy is most useful in the wrought'form, such as sheets, due to its formability characteristics, it may also be suitably used in making castings, forgings, extruded forms, and the like.

The new alloy may be compounded in any of the ways known to the art, such as by adding the alloying ingredients to the molten magnesium under a suitable flux. The flux should be substantially free from magnesium chloride if the barium content of the alloy is to be above about 0.4 per cent. In those instances where an alloy is to be compounded containing less than 0.4 per cent barium, magnesium chloride may be present in the flux without exerting a deleterious effect,

but in this case it is usually desirable to add the barium last and without too much stirring in order that the loss of barium into the flux will be substantially prevented.

We claim:

1. A magnesium base alloy containing from 0.05 to 1 per cent of barium and from 0.1 to 3 per cent of manganese, the balance being magnesium.

2. A magnesium base alloy containing from 0.1 to 0.4 per cent of barium and from 1 to 2 per cent of manganese, the balance being magnesium.

3. A magnesium base alloy containing 0.2 per cent of barium and from 1 to 2 per cent of manganese, the balance being magnesium.

JOSEPH n. HANAWALT. JOHN c. MCDONALD. 

